Work in progress concerns: (1) structural and metabolic relationships among human plasma lipoproteins, (2) lipoprotein abnormalities in disease states (homozygous IIa and nephrotic IIa hyperlipoproteinemias, beta-sitosterolemia, and cerebrotendinous xanthomatosis (CTX) in which atherogenesis and deposits of sterols in peripheral tissues are increased, and (3) relation of composition and/or structure to physiological functions and metabolism of the lipoproteins. We are comparing normal and abnormal lipoproteins with respect to heterogeneity, morphology, surface structure, apolipoprotein and lipid compositions, and molecular interactions. The work includes further characterization of specific apolipoproteins, including the basis of polymorphism and the effect of structural variation on lipid binding and other functions of the proteins.